The CIA staged a mock execution and brandished weapons, including a gun and a power drill, during interrogation sessions with detainees the agency was desperate to persuade to talk, according to a long-secret internal CIA report expected to be released Monday.

The episodes are part of a catalog of alleged abuses -- a 2004 report by the CIA's inspector general -- that has prompted U.S. Atty. Gen. Eric H. Holder Jr. to consider appointing a criminal prosecutor to investigate cases in which the CIA strayed beyond its interrogation authorities.The prisoner confronted with the gun and power drill was identified by current and former U.S. government officials as Abd al-Rahim al-Nashiri, the alleged plotter of the attack on the USS Cole. Nashiri was also one of three prisoners who was subjected to the simulated drowning interrogation method known as water-boarding.

The IG report also describes at least one instance in which the CIA fired a gunshot in a room next door to a detainee in an apparent effort to convince the prisoner that another terrorism suspect had been executed, the official said.

Some of the allegations, including the presence of a gun in an interrogation room, have been previously reported. But some of the details disclosed this weekend, including the name name of the detainee, are new.

The cases are among the most extreme examples in which CIA interrogators sought to improvise methods that were never mentioned in any of the legal memos the agency procured from the Justice Department authorizing the so-called enhanced interrogation program.

"Some of the things that were done were almost in juvenile detective mode," said a former U.S. official familiar with the contents of the report.

Even so, the IG report focused most of its most critical attention on alleged abuses of interrogation methods the agency had been explicitly authorized to use. In particular, the report raised troubling questions about the frequency with which certain prisoners were being water-boarded.

Segments of the IG report that were declassified earlier this year indicate that two senior Al Qaeda prisoners -- Khalid Sheikh Mohammed and Abu Zubayda -- were water-boarded a total of 266 times, far more than had been envisioned in the Justice Dept. memos that gave the CIA permission to use the harsh method.The CIA declined to discuss specifics in the report, which has yet to be publicly released.

But CIA spokesman Paul Gimigliano said that the Justice Department has had the complete IG report since 2004 and that prosecutors have carefully reviewed it for legal accountability.

He said the CIA "in no way condoned behavior -- no matter how infrequent -- that went beyond formal guidance."

"This has all been looked at," Gimigliano added. "Professionals in the Department of Justice decided if and when to pursue prosecution. That's how the system was supposed to work and that's how it did work."

Still, Holder is said to be moving closer to appointing a criminal prosecutor to examine, or in some cases, re-examine cases of alleged CIA interrogation abuse. The disclosure of fresh details from the report this weekend was seen by some in Washington as a sign that Holder may be setting the stage for such an announcement.

The details on the mock execution and the use of the power drill were first reported online on Friday by Newsweek. The CIA's use of a gun in the booth with a prisoner was first disclosed by The Times/Tribune earlier this month.